It is expected that an acid generator for a photoresist material has a molecular structure which can absorb ultraviolet rays or light having bigger energy than ultraviolet rays and has a bond which can generate an acid after excitation due to the light absorption. As such acid generators, onium salt compounds, oxime compounds, amide compounds, imide compounds, and the like are known. For example, sulfonic esters, the aromatic part of which is unsubstituted, are known as the imide compounds (see the patent document 1 below, for example).